i can not say if the site is a scam currently if they suddenly pay some of their members.
now i can not find the article,but the main idea of the article is saying that each ptc can have only one or two real sponsors and most of them do not have even one.and when there is a big mount of members in the site then admins can only pay there members with the money from the following upgrades and buying referals.and it is also the problem of those admins.